Conventionally, the mold step for a semiconductor package has been carried out in such a manner that, in a region adjacent to a die cavity, a lead frame which has leads and dam bars connecting the leads is sandwiched between the lower die half and upper die half of the mold die, and a resin or ceramic is injected into the die cavity for molding.
In this process, as shown in FIG. 3 and FIG. 4 of patent Document 1, resin, or the like, remains between the dam bar and a seal. This is because, in the mold step, the dam bar is positioned outwardly away from the die cavity by a predetermined distance, so that the resin, or the like, leaks in a space surrounded by the upper and lower die halves of the mold die and the dam bar. After the completion of the mold step, the dam bars connecting the leads are cut in order to break the electrical connections between the leads. It has been known, however, that the residual resin (or ceramic) has small adhesivity to the leads and therefore readily falls off, thereby causing various defects.
For example, in patent Document 1, a dam bar is cut by using a resin cut die with an elastic element such that the residual resin is removed away together with the dam bar as shown in FIG. 2 of this publication.
According to a method illustrated in FIG. 1 of patent Document 2, a dam bar is cut with a side edge of a die part which supports a lead part present between the dam bar and a seal being positioned inner than a side edge of the lead, such that part of the residual resin remains. The remaining resin part is removed later by an elastic element, or the like.                Patent Document 1: Japanese Laid-Open Patent Publication No. 7-193095        Patent Document 2: Japanese Laid-Open Patent Publication No. 2003-17643        